Dressed in heavy overalls against a cold wind, members of the National Transportation Safety Board (NTSB) spent all day yesterday at the crash site, picking through the wreckage not only for the victims but for identifiable pieces of the shattered aircraft.

Investigators cautioned that there will be no quick explanation why no one was conscious at the controls for four hours on Monday, when the jet flew 2,250 kilometres across the country before running out of fuel and slamming nose-first into the ground.

The plane had no flight data recorder that could yield information on the aircraft and its performance. It had a cockpit voice recorder, but it consisted of a 30-minute loop that usually records over itself. And Stewart and the others on the plane presumably werealready unconscious or dead by the last half-hour of the flight. The cockpit recorder had not been found as of last night.

Most of the plane's debris is embedded in mud and soil within a three-metre-deep, nine-metre-wide crater said Bob Francis, vice chairman of the NTSB.

``It looks like the aircraft was pretty much vertical when it hit the ground,'' Francis said. ``The ground is soft, and it went in fairly deep. It's going to be a challenge, with the wreckage and sorting out what's there.''

Brad Randall, a state medical examiner, said toxicology tests may be worthless in attempting to verify one possible theory for the accident -- that the victims suffered oxygen deprivation because of a sudden decompression of the aircraft.

If a plane loses cabin pressure, pilots are supposed to put on oxygen masks and quickly descend to 3,600 metres or lower. There was no evidence suggesting the pilots of Stewart's jet made any effort to do so, but Francis declined to speculate what that could mean.

On Monday,Air Traffic Controllers were unable to raise anyone aboard the plane by radio soon after it took off from Orlando, Florida. Fighter pilots who chased it were unable to see into the plane because its windows were frosted over, indicating the temperature inside was well below freezing.

Francis confirmed that the crew of one of the fighterjets made a videotape of the Lear jet. ``It appears that the video was taken through a heads-up display on the aircraft, and the quality is probably not going to be good enough to help us,'' he said.

Officials said the air temperature at the altitude the jet was flying would have been well below freezing. Together, the evidence raised suspicions that the plane had experienced a catastrophic loss of cabin pressure.

Four years ago, federal regulators ordered that valves that regulate pressure on Lear jets be replaced to ``prevent rapid decompression of the airplane.'' The Federal Aviation Administration (FAA) gave owners 18 months to comply.

James Watkins, president ofSunjet Aviation Inc., which operated the jet, told The Washington Post for a story in today's editions that the aircraft's maintenance log books showed that the new valves had been installed.

Memorial service

ORLANDO: A memorial service for Stewart will be held on Friday at the first Baptist church of Orlando, where Stewart attended services and where his children go to day school. Stewart recently donated $ 500,000 to the church.

While Stewart's family made plans for the service, friends continued to pay their respects at the Stewarts' mansion in the Windermere community, about 16 kilometres southwest of Orlando. A steady stream of people came to comfort Stewart's wife, Tracey, and their children, 13-year-old Chelsea and 10-year-old Aaron.

PGA Tour tribute

HOUSTON: Competition in two PGA Tour events will be postponed on Friday because of the memorial service for Stewart.

The Tour Championship in Houston, a $ 5 million event for the top 30 players on the tour's money list,will start tomorrow with 27 holes. Another 27 holes will be played on Saturday, with the 18-hole final round on Sunday.

The Tour Championship needs to end by Sunday because of travel plans. The entire field is eligible for the World Golf Championship event next week in Spain.

At the Champions Golf Club, flags were at half-staff. Smiles were hard to find. Tiger Woods felt a void when he watched the developments unfold on television on Monday, the Lear jet with Stewart and five others aboard, flying uncontrolled across the heartland, only a matter of time before it ploughed into the earth.

It hit Woods even harder when he flew to Houston that night and picked up the Pro-Am pairing. His tee time was 9 am -- a slot below, which once held Stewart's name -- was blank.

``That was a rude awakening,'' Woods said. ``You think that hopefully it was a bad dream, a nightmare... But unfortunately, it came true. It's hard to be believe he's not going to be here.''

A lucky escape

RALEIGH: Neither manplanned to fly with Stewart. But one boarded the plane and died, and the other didn't, living to grieve his friend's death.

Mike Hicks had been Stewart's caddie for 12 years. He probably would have been a passenger on that doomed flight had not his family accompanied him from their home in Mebane to Orlando, Florida, for the Disney tournament last weekend.

Hicks flew home with his wife and three children instead of flying with Stewart to Texas. His wife, Meg, almost balked at the trip because it was a big job travelling with young children, Hicks' mother, Faye, said.